1. Field of the Invention
The present invention relates to a disc chucking mechanism which rotates, together with a turn table, a recording medium disc, such as an optical disc or a magneto-optical disc, to be located on the turn table, to write information into the recording medium disc and read it from the same. More particularly, the invention relates to a disc chucking mechanism for positioning a disc with a magnetic center hub and holding the same.
2. Related Art
In a disc drive which writes information signals into a recording medium disc, such as an optical disc or a magneto-optical disc, or reproducing stored information from the same while rotating the recording medium disc, the disc must be rotated in a state that an optical pickup device faces a recording track on the disc.
Therefore, the disc drive is provided with a disc chucking mechanism including a turn table. A rotation driving mechanism drives and rotates the turn table, together with a disc being put on the turn table at a predetermined location. Examples of the conventional the disc chucking mechanism are U.S. Pat. No. 5,501,760 and Unexamined Utility Model Publication Hei.4-131178.
In the disc chucking mechanism disclosed in U.S. Pat. No. 5,501,760, a chucking magnet is mounted on a turn table, and a magnetic force exerting between the chucking magnet and the center hub of the disc is utilized to attract a disc to the turn table. The chucking magnet is bonded onto the turn table by adhesive.
In the disc chucking mechanism disclosed in Unexamined Utility Model Publication Hei.4-131178, a hub table substantially integral with the turn table is shaped so that the chucking magnet is sandwiched between the hub table and the turn table, whereby the chucking magnet is fastened onto the turn table.
In the disc chucking mechanism by utilizing the magnetic force between the disc and the center hub, to fasten the chucking magnet for generating a magnetic attraction force to the turn table, adhesive is used or the turn table or the hub table are specially designed in shape.
The technique using adhesive (first technique) is disadvantageous in that the fixing strength is unsatisfactory, and that a subtle difference of adhesion condition results in a large variation of adhesion strength, leading to deterioration of a reliability of the disc chucking mechanism.
The technique (second technique) in which the chucking magnet is mechanically fixed is advantageous over the first technique in that a sufficient fastening strength is secured, and provides a reliable disc chucking mechanism, but disadvantageous in that the component part is specially designed, and its shape is complicated, leading to increase of its manufacturing cost.